Pneumatic telescoping cylinder and method

A double acting telescoping cylinder extensible and collapsible responsive to the application of air under pressure, comprising:

• a housing having an external cylindrical wall;
• an end cap closing one end of said cylindrical wall;
• a central piston having a central opening facing said end cap;
• a central hollow piston rod extending outwardly from said central piston away from said end cap in axial alignment with said central opening and with said cylindrical wall and terminating at a terminating wall having a face remote from said central piston and facing said end cap;
• a first port through a first end of said cylindrical wall adjacent said end cap communicating with said central piston, central hollow piston rod and terminating wall face;
• a concentric piston and concentric piston rod having a hollow interior portion containing said central piston and central hollow piston rod respectively;
• said central piston carrying said central hollow piston rod to extended position remote from said end cap whereupon movement of said concentric piston and concentric piston rod is initiated through exposure of a face of said concentric piston facing said end cap to air pressure from said first port;
• said external cylindrical wall terminating at an end wall remote from said end cap, said end wall extending radially inwardly with respect to an inner cylindrical surface of said external cylindrical wall, said end wall having an end wall face facing said end cap;
• a second port through said external cylindrical wall, said second port extending perpendicular to said end wall face and straddling said end wall face;
• an air opening in said concentric piston rod aligned with said second port when said concentric piston is retracted and adjacent said end cap for connecting said hollow interior portion in said concentric piston and piston rod with said second port;
• whereby application of air pressure to said first port causes said central piston and central piston rod to be extended followed by extension of said concentric piston and concentric piston rod from the cylindrical wall, and whereby application of air pressure to said second port causes retraction of the concentric piston and concentric piston rod followed by retraction of said central piston and central piston rod toward said end cap.